From: Alistair Popple Date: Thu, 19 Jun 2025 08:57:56 +0000 (+1000) Subject: mm: convert vmf_insert_mixed() from using pte_devmap to pte_special X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4b1d3145c1045d4b0db4622cd2c224a247f25a20;p=thirdparty%2Flinux.git mm: convert vmf_insert_mixed() from using pte_devmap to pte_special DAX no longer requires device PTEs as it always has a ZONE_DEVICE page associated with the PTE that can be reference counted normally. Other users of pte_devmap are drivers that set PFN_DEV when calling vmf_insert_mixed() which ensures vm_normal_page() returns NULL for these entries. There is no reason to distinguish these pte_devmap users so in order to free up a PTE bit use pte_special instead for entries created with vmf_insert_mixed(). This will ensure vm_normal_page() will continue to return NULL for these pages. Architectures that don't support pte_special also don't support pte_devmap so those will continue to rely on pfn_valid() to determine if the page can be mapped. Link: https://lkml.kernel.org/r/93086bd446e7bf8e4c85345613ac18f706b01f60.1750323463.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple Reviewed-by: Jason Gunthorpe Reviewed-by: Dan Williams Cc: Balbir Singh Cc: Björn Töpel Cc: Björn Töpel Cc: Christoph Hellwig Cc: Chunyan Zhang Cc: David Hildenbrand Cc: Deepak Gupta Cc: Gerald Schaefer Cc: Inki Dae Cc: John Groves Cc: John Hubbard Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Will Deacon Signed-off-by: Andrew Morton --- diff --git a/mm/hmm.c b/mm/hmm.c index d0c5c35807a23..14914da98416d 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -302,13 +302,10 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, goto fault; /* - * Bypass devmap pte such as DAX page when all pfn requested - * flags(pfn_req_flags) are fulfilled. * Since each architecture defines a struct page for the zero page, just * fall through and treat it like a normal page. */ if (!vm_normal_page(walk->vma, addr, pte) && - !pte_devmap(pte) && !is_zero_pfn(pte_pfn(pte))) { if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) { pte_unmap(ptep); diff --git a/mm/memory.c b/mm/memory.c index ea1388d2a87a7..01d51bd95197d 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -598,16 +598,6 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, return NULL; if (is_zero_pfn(pfn)) return NULL; - if (pte_devmap(pte)) - /* - * NOTE: New users of ZONE_DEVICE will not set pte_devmap() - * and will have refcounts incremented on their struct pages - * when they are inserted into PTEs, thus they are safe to - * return here. Legacy ZONE_DEVICE pages that set pte_devmap() - * do not have refcounts. Example of legacy ZONE_DEVICE is - * MEMORY_DEVICE_FS_DAX type in pmem or virtio_fs drivers. - */ - return NULL; print_bad_pte(vma, addr, pte, NULL); return NULL; @@ -2483,10 +2473,7 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr, } /* Ok, finally just insert the thing.. */ - if (pfn_t_devmap(pfn)) - entry = pte_mkdevmap(pfn_t_pte(pfn, prot)); - else - entry = pte_mkspecial(pfn_t_pte(pfn, prot)); + entry = pte_mkspecial(pfn_t_pte(pfn, prot)); if (mkwrite) { entry = pte_mkyoung(entry); @@ -2597,8 +2584,6 @@ static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn, bool mkwrite) /* these checks mirror the abort conditions in vm_normal_page */ if (vma->vm_flags & VM_MIXEDMAP) return true; - if (pfn_t_devmap(pfn)) - return true; if (pfn_t_special(pfn)) return true; if (is_zero_pfn(pfn_t_to_pfn(pfn))) @@ -2630,8 +2615,7 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, * than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP * without pte special, it would there be refcounted as a normal page. */ - if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && - !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) { + if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pfn_t_valid(pfn)) { struct page *page; /* diff --git a/mm/vmscan.c b/mm/vmscan.c index 56d540b8a1d0c..6698fadf5d047 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3425,7 +3425,7 @@ static unsigned long get_pte_pfn(pte_t pte, struct vm_area_struct *vma, unsigned if (!pte_present(pte) || is_zero_pfn(pfn)) return -1; - if (WARN_ON_ONCE(pte_devmap(pte) || pte_special(pte))) + if (WARN_ON_ONCE(pte_special(pte))) return -1; if (!pte_young(pte) && !mm_has_notifiers(vma->vm_mm))